Automatic power control system



Dec. 27, 1955 w. T. J. DAY ET AL 2,728,865 AUTOMATIC POWER CONTROLSYSTEM Filed Nov. 5, 1951 3 Sheets-Sheet l r \42 I gg l E WALTER I J.DAY

' BENJAMIN LEVINE F I6 I WILLIAM E. SABLESAK BY Affarr/e Dec. 27, 1955w. T. J. DAY E L AUTOMATIC POWER CONTROL SYSTEM 3 Sheets-Sheet 2 FiledNov. 5, 1951 FIG.2

WALTER T J. DAY BENJAMIN LEVI NE WILLIAM E. SABLESAK Dec. 27, 1955 w. T.J. DAY ET AUTOMATIC POWER CONTROL SYSTEM 3 Sheets-Shet 3 Filed NOV. 5,1951 K A B E M mm HM S J LE.

R N A M EU V mm WW 8W WWM iffy/787 United States Patent 2,728,865AUTOMATIC POWER CONTROL SYSTEM Application November 5, 1951, Serial N 0.254,966 7 Claims. (Cl. 39780) (Granted under Title 35, U. S. Code(1952), see. 266) The invention described herein may be manufactured andused by or for the Government for governmental purposes, without thepayment of any royalty thereon.

This invention relates to power switching systems and more particularlyto power switching systems wherein automatic switching from a primary toan auxiliary source is accomplished upon failure of the primary source.

An object of this invention is to provide an automatic switching meanswhich positively switches an auxiliary power source into a circuit uponfailure of a primary source.

A further object of this invention is to provide for con trol means bywhich choice of primary and auxiliary source may be changed afteroperation has begun.

Former switching circuits known to the art have definitely predeterminedprimary and auxiliary sources, wherein the auxiliary source intendedmerely for emergency use in the event of primary source failure, andusually provide for automatic reconversion to primary source use uponnormal conditions returning to the primary source. It is a furtherobject of this invention to provide a switching system for a pluralityof sources whereby continued operation can be obtained through alternateoperation of so that no particular source will be automatically favoredby the switching system.

A further object of this invention is to provide for manual control ofthe automatic transfer system.

A further object of this invention is to provide an automatic switchingsystem capable of remote control supervision.

Another object of this invention is to provide an improved automaticswitching system in which either one of at least two power sources canbe initially energized, and which, upon the failure of the initiallyenergized power will cause the other power source to be activated.

yet preserving the automatic power source and load transfers.

These and further objects of this invention will appear in the followingdescription and appended claims, reference being had to the appendeddrawing consisting of one figure.

In the appended drawing, consisting of three figures, one embodiment ofthe switching system as it could be used with single phase A. C. powersources is shown. It is obvious to those skilled in the art that, withslight modithe same system could be made to control poly- C. circuits,but, for the sake of simplicity, a single phase A. C. network is hereshown.

In the drawing, power source generators 2 and 4 are shown mechanicallyconnected to prime movers 6 and 8,

respectively. Prime movers 6 and 8 are shown connected to motor controlmeans 10 and 12, respectively. Motor control means 10 and 12 may be ofany standard type known to the art and, because they are not part of theinvention here, they are indicated and not described. Motor controlmeans 10 is electrically connected to and controlled by start relay 14and stop relay 16. Motor control means 12 is electrically connected toand controlled by start relay 18 and stop relay 20.

In the drawing, all relay arms are shown in their normal position withpower sources 2 and 4 inoperative and electrically connected as follows.Power source 2 is connected through normally open arms 22 and 24 ofrelay 26 to load 28. Coil 36 of relay 26 is paralleled across powersource 2 by means of switch 32 and arm 34 of relay 26. Power source 4 isconnected through normally open arms 36 and 38 of relay 26 to load 28.Coil 40 is paralleled across power source 4 by means of switch 42 andarm 44 of relay 26. Coil 46 of relay 48 is connected to and derives itspower from power source 2 through rectifier 50, transformer 52 and lead54. Transformer 52 is conpower source 2 through lead 54, arm 56 ofconnected to and derives its power from power source 4 through rectifier64, transformer 66 and lead 68. Transormer 66 is connected across powersource 4 lead 68, arm 69 of relay 8t) and switch 42. Coil 72 of manualstart relay 58 is connected to D. C. source 74 through switch 42 andderives its operative round through selector switch 76 and either arm 78of relay 80 and ay 86 and selector switch 76. Coil 102 of relay 86 isconnected relay 86, upon operating, locks itself to ground through itsown arm 108, arm of relay 98 arm 112 of relay 80 and selector switch 76.Coil 114 of nectcd to D. C. source 74 through switch 52 and derives itsoperative ground through start-stop button 82.

114 of relay 98, two other grounding circuits are provided to providefor time delay in the opening of relay 98 during the time that theoperating power source is being de-energized. These circuits areprovided by relays S0 and 86, depending on whether power source 2 or 4is operating. If power source 2 is operating, coil 114 is groundedthrough arm 115 of relay 98 and arm 117 of: relay 80; and if powersource 4 is operating, coil 114 is grounded through arm 115 of relay 93and arm 115* of relay 86.

Start and stop relays 14, 16, squares in the drawing, are so connectedto a power source (not shown) that they will operate as soon as they aregrounded. The operative ground connections of these relays are asfollows. When selector switch 76 is in its lower position and start-stopbutton 82 is pressed 18 and 20, indicated by to its start position,start relay 14 is connected to ground through arm 116 of relay 80,selector switch 76 and arm 11%: of relay 58. In the event of powerfailure in power source 2, and while selector switch 76 is in its lowerposition, start relay 18 is connected to ground through arm 12% of relayS6, arm 122 of relay 8i), arm 124 of relay 48 and arm 126 of relay 98.

When selector switch 76 is in its upper position and start-stop button82 is pressed to its start position, start relay 18 is connected toground through arm 126 of relay $6, selector switch 76 and arm llS ofrelay 53. in the event of power failure in power source and whileselector switch 76 is in its upper position, start relay is connected toground through arm 116 of relay c'ill, arm 12% of relay 86, arm 130 ofrelay 62, and arm 126 of relay 93. When start-stop button 82 is pressedto its stop position, relay 98 operates so that stop relay 16 isgrounded through switch 32 and arm 132 of relay 96 and stop relay 20 isgrounded through switch &2 and arm 334 of relay 98.

Auxiliary grounding circuits are provided for stop relays in and 2t) sothat there is no possibility that one power source will cut in while theother is in operation. The auxiliary grounding circuit for stop relay 16is provided by relay 62 which causes stop relay 16 to be connected toground through switch 32, arm 136 of relay arm 13% of relay 62 and arm126 of relay 98, when power source 4 is operating. The auxiliarygrounding circuit for stop relay 29 is provided by relay 48 which causesstop relay 20 to be connected to ground through switch 42, arm 140 ofrelay 62, arm 142 of relay 4%, and arm 126 of relay 98.

in the operation of a system according to this invention, switches 32and 42 are closed at all times. Said switches are not necessary to thesystem, but are merely provided as a safety feature. A choice is firstmade as to which of the two power sources 2 and 4 is to be used as aprimary source. Selector switch 76 is then manually placed in a positioncorresponding to this choice. Assuming that it is desired to use powersource 2 as a primary source, selector switch 76 is closed in its lowerposition. Startstop button 82 is then placed in its start position. Theplacing of start-stop button 82 in its start position energtzes relay 58through the circuit D. C. source 74, coil 72 of relay 5'3, selectorswitch 76, arm 84 of relay 36 and start-stop button 82. Relay 53 thenoperates connecting ground to start relay 14 through arm 116 of relaythe, selector switch 76 and arm 118 of relay 58. Start relay 14 thenoperates through motor control to start prime mover 6 and thus activatepower source generator 2. Power source 2 then activates coil 3% of relay26 through the circuit: switch 32, coil 3d, and arm 34- of r i 26. Theoperation of coil connects power source to load 28 through arms 22 and24 of relay 26 and breaks the contact made by arm 44 of relay 6 so thatpower source 4 has no possibility of being across load 23. Once powersource 2 is operating properly, start-stop button 82 is released whichremoves ground from coil 72 of relay 58. This causes the conela 2 tactorarms of relay 58 to return to the position shown in the drawing whichconnects the power developed by power source 2 to transformer 52 througharm 56 of relay 5% and switch 32. Transformer 52, through rectifier 59,then supplies D. C. power to coil 46 of relay 48, causing relay 4% tooperate. The operation of relay 43 connects ground to stop relay 20 ofmotor 3 through arm 14% of relay 62, arm 142 of relay 48, and arm 126 ofrelay 93, thus preventing motor 8 and, consequently, power source 4%,from operating. Further, the operation of relay 48 serves to operaterelay fill by grounding coil 83 through arm 2% of relay 58 and arm 92 ofrelay 43. When relay 8% operates, it locks coils 88 across D. C. supply74 and ground through the circuit, D. C. supply 74-, switch 42, coil 38,arm 94 of relay 30, arm 96 of relay 98, arm 10%) of relay 86 andselector switch ground to be connected 76. At this time the system hascompleted its starting cycle and power source 2 is supplying the load23.

In the event that power source 2 fails or its output falls below apredetermined level, the system of this invention causes power source 4to be switched into operation in the following manner. The loss ofvoltage by power source 2 causes coil 36 of relay 26 to becomeinoperative, which breaks the contacts of arms 22 and 24 of relay 26 andremoves load 23 from power source 2. Fur ther, the inoperative characterof coil 30 causes arm 44 of relay 26 to connect coil it) of relay 26across power source 4 through the circuit, arm 44 of relay 26, coil asof relay 26, and switch 42. At the same time, the failure of voltage inpower source 2 causes coil to of relay 4?; to become inoperative,returning the contact arms of relay 48 to the position shown in thedrawing. The opening of arm 142 of relay 48 removes ground from stoprelay 20. The closing of arm 1240f relay causes to start relay 18through said arm 124, arm 122 of relay 80 and arm 120 of relay 36. Startrelay 18 then starts prime mover 8 tirough motor control 12. Powersource 4 then begins operation. Power source 4 supplies power to coil 4%of relay 26, closing arms 36 and 38 and opening arm 34- of relay 26.Arms 36 and 38 of relay 26 then connect power source 2 to load 28. Theopening of arm 34- of relay 26 opens the circuit of coil 39 of relay 26so that power source 2 can not develop voltage and place itself back onload 28. Also, when power source 4 begins opera tion, it supplies powerto transformer 66 through arm of relay 58 and switch 42. Transformer 66,through rectifier 64, then supplies D. C. power to coil 60 of relay 62,causing relay 62 to operate. The operation of relay 62 connects groundto stop relay 16 of motor 6 through arm 136 of relay 48, arm 138 ofrelay 62 and arm 126 of relay 98, thus preventing motor 6 and,consequently, power source 2, from operating. Further, the operation ofrelay 62 serves to operate relay 86 by grounding cell 102, through arm104 of relay 58 and arm 1 56 of relay 62. Further, the operation ofrelay S6 opens arm The of relay 86, thus opening the lock circuit ofrelay 8t) and causing relay to release. The fact that selector witch 76is in its lower position prevents relay 86 from locking itself to D. C.source 74 and ground, thus making the operative condition of relay S6dependent the continued operation of power source 4. The dependence ofrelay-86 on power source 4 therefore prevents the system from attemptingto switch back. to power source 2 operation, in the event of powerfailure in power source 4 because the system is symmetrical, so thatjust as switching from power source 2 to power source 4 was dependent onrelay 8! remaining operative through its selector switch lockin, sowould automatic switching from power source 4 to power source 2 bedependent upon the continued operation of relay 86.

111 the event that the diificulty that caused power source 2 to fail iscorrected, and it is desired to cause the system to transfer the load topower source 2 when power source 4 fails, selector switch 76 may bethrown to its upper position which provides a lock-in circuit for coil262 of relay 86 as follows: D. C. source 74, switch 42, coil 162, arm198 of relay 86, arm lid of relay 9%, arm 112 of relay 80 and selectorswitch "76. The system will then cause load 28 to be switched to powersource 2 in the event that power source 4 fails in the same manner asthe load was automatically transferred from power source 2 to powersource 4 when power source 2 failed, the only diiference being that thecorresponding parts of the symmetrical circuit will be utilized.

The system, according to this invention, also provides a manual transferfeature which can be used to switch from one power source to the otherwithout waiting for power failure in the power source that is supplyingthe load. To illustrate this feature, assume that power source 2 issupplying load 28 and that it is desired to transfer to power source 4,then coil 30, relay 26, relay 48, and relay 8t would be operative, andcoil 40, relay 26, relay 62, and relay 86 would be inoperative, as shownin the drawing, and selector switch 76 would be in its lower position.To initiate manual transfer, start-stop button 82 is pushed to the startposition which completes the supply circuit of coil 72 of relay 58through selector switch 76, arm 84 of relay 86, and start-stop button82. Coil '72 then operates relay 58. When relay 58 operates, arm 56opens the circuit of coil 46 of relay 48, causing reiay to becomeinoperative. When relay 48 becomes inoperative, arm 142 opens thecircuit of stop relay 20 to ground and acting through arm 124 of relay48, arm 122 of relay 80, and arm 120 of relay 86, grounds start relay18. Start relay 18 starts prime mover 8 by means of motor control 12,which causes power source 4 to operate.

Power source 4 then supplies power to coil 60 of relay 62. It should benoted that the circuit of coil 60 utilizes the auxiliary contactsprovided by arm 69 of relay 80 in order to complete its circuit becauseits normal circuit through arm 70 of relay 58 is not available, due tothe operative condition of relay 58 caused by start-stop button 82 beingin the start position. Coil 60 operates relay 62 which places ground onstop relay 16 through arm 138, thereby causing power source 2 to becomeinactive.

The inactive character of power source 2 causes coil 38 of relay 26 tobecome inactive which opens contact arms 22 and 24, removing powersource 2 from load 28. Further, arm 44 of relay 26 closes when coil 30loses its voltage, thus placing coil 40 of relay 26 across power source4. Power source 4 then supplies coil 40, which closes arms 36 and 38 ofrelay 26 Connecting power source 4 to load 28. Coil 40 also operates arm34 of relay 26, which disconnects coil 30 from power source 2 andprevents the possibility of power source 2 going back across load 28, incase power source 2 develops voltage.

The operation of relay 62 also completes the power circuit to coil 102of relay 86 through arm 106, if startstop button 82 has been released.If start-stop button 82 has not been released, then relay 62 remainsineifective with regard to coil 102, but will serve to energize coil 102just as soon as start-stop button 82 is released and arm 104 of relay 58returns to its normal closed position. Once coil 102 is energized, itoperates relay 86 which, through the opening of arm 100, unlocks coil 88of relay 89 from its lock-in circuit. When coil 88 loses its energy,relay 80 releases and the action of the system is complete.

From the foregoing explanation of system operation and the parts playedby selector switch 76 and relays 80 and 86, it can be seen that one andonly one transfer of power sources, either automatic or manual, may bemade through this system unless, and until, selector switch 76 isreversed after a transfer, in order to set up the next transfer.

At any time during the operation of a system according to thisinvention, that it is desired to disconnect all power sources from theload, start-stop button 82 is pushed to its stop position. Thiscompletes the power circuit of coil 114 of relay 98. Coil 114 thenoperates relay 98 which places ground on stop relay 16 through arm 132and switch 32 and connects ground to stop relay 2%? through switch 42and arm 134. Also, in order that the system will respond to aninstantaneous push of the start-stop button 82 when it is pushed to thestop position, an auxiliary hold circuit is provided by arm 115 actingin conjunction with arm 117 of relay 80 or arm 119 of relay 86,depending on whether relay 80 or relay 86 is operated.

An auxiliary or remote control switch panel 144 is shown to illustratethe adaptability of this system to remote control techniques. Terminalboard 146 is provided with terminals 148, 150, 152, 154, 156, 158 and '6160 which correspond to terminals 162, 164, 166, 168, 170, 172 and 174,respectively, of terminal board 176. Start button 178 is connected topoints common with the connections of start-stop switch 82 and itsfunction is the same as that of start-stop switch 82 with respect tostarting the operation of the system or with respect to initiatingmanual transfer. Stop button 180 is con nected to points common with theconnections of startstop switch 82 and its function is the same as thatof start-stop switch 32 with respect to stopping the operation of thesystem. Lights 182 and 184 are provided in remote control panel 144 toindicate the operation of power sources 2 and 4. Light 182 is connectedacross power source 2 through terminals 148 and 162, switch 32, andterminals 164 and 150. Light 184 is connected across power source 4through terminals 158 and 172 and switch 42 and terminals 174 and 160.Thus, when either power source 2 or 4 is operating, its correspondinglight operates at the remote control panel 144 to apprise the operatorof the operative condition of the power source.

The system according to this invention as shown and described, isapplied to a single phase two power source system, however, thoseskilled in the art will readily appreciate the adaptability of thesystem to multiphase circuits employing more than two power sources.Accordingly, it is to be understood that the invention is not limited toits specific embodiments, except as defined in the appended claims.

What is claimed is:

1. In a power switching system, the combination comprising a first andsecond motor generator set, a load circuit, a first relay having a firstand second winding for connecting said first and second generators,respectively, to said load, the first and second winding of said firstrelay being connected across said first and second generatorsrespectively, said first winding of said first relay being connectedthrough one normally closed arm of said second winding of said firstrelay and said second winding of said first relay being connectedthrough one normally closed arm of said first winding of said firstrelay; means for starting said motor-generator sets comprising aninitiating switch, an initiating relay connected to be energized throughsaid initiating switch, a multiple position selector switch, connectedto said initiating relay, a first pair of relays connected to saidselector switch and controlled thereby, a second pair of relaysconnected to said first pair of relays and energized through said firstpair of relays, and a pair of motor controls operated by said secondpair of relays; means for automatically transferring said load betweensaid motor-generator sets when the voltage of the load connectedgenerator falls below a predetermined level comprising a third pair ofrelays, the first and second relays of said third pair of relays beingvoltage actuated by said first and second motor-generator setsrespectively, the first and second relays of said third pair of relayshaving arms through which the first and second relays of theaforementioned first pair of relays are respectively actuated when saidfirst and second relays of said third pair of relays are respectivelyactuated, the aforementioned multiple position selector switch connectedintermediate said first pair of relays so that in a first position itcompletes a lock-in circuit for the first relay of said first pair ofrelays and in a second position it completes a lock-in circuit for thesecond relay of said .first pair of relays; and means for stopping saidmotorgenerator sets comprising the aforementioned pair of motor controlsand a fourth pair of relays, the first and second relay of said fourthpair of relays connected, respectively, to the first and second motorcontrol of said pair of motor controls for operating said motorcontrols, said fourth pair of relays being connected to and energizedthrough the aforementioned third pair of relays.

2. In a power switching system according to claim 1, means for stoppingsaid motor-generator sets comprising a stopping switch and a stoppingrelay connected to be energized through said stopping switch, saidfourth pair 'of relays being connected to and energized through saidstopping relay.

3. A power transfer system in which any one of at least two powersources can be the primary source of power, comprising at least twopower sources, first means for selectively energizing any one of saidpower sources, second means coupled through said first means to theoutput of said one power source and responsive thereto for energizingsaid other power source when said one power source is not operatingnormally, third means coupled through said first means to the output ofsaid other power source and responsive thereto, when said first meansselects said other power source to be initially energized, forenergizing said one power source when said other power source is notoperating normally, fourth means coupled to the output of said one powersource and responsive thereto for connecting a load circuit thereto whensaid one power source is operating normally, and fifth means coupled tothe output of said other power Source and responsive thereto forconnecting said load circuit thereto when said other power source isoperating normally, said fourth and fifth means being interconnected sothat the operation of either one prevents the operation of the other,said second and third means being coupled together through said firstmeans so as to prevent the reenergization of the initially energizedpower source after the other power source has been energized.

4. A power transfer system in which any one of at least two powersources can be the primary source of power, comprising at least firstand second power sources, an initiating relay, a multiple positionselector switch coupled to said initiating relay for coupling either oneof said power sources to said initiating relay to selectively energizeone of said power sources, said first power source having associatedtherewith a first relay responsive to the output thereof and coupled tosaid selector switch and said second power source, said first relayenergizing said second power source only when said first power sourcefalls below a predetermined level after being initially activated, saidsecond power source having associated therewith a second relayresponsive to the output thereof and coupled to said selector switch andsaid first power source, said second relay energizing said first powersource only when said second power source falls below a predeterminedlevel after being initially acti vated, a third relay associated withsaid first power source and responsive to the output thereof forconnecting a load circuit thereto, and a fourth relay associated withsaid second power source and responsive to the output thereof forconnecting said load circuit thereto, said third and fourth relays beinginterconnected so that the operation of either one prevents theoperation of the other, said first relay being coupled to said secondrelay through said selector switch so as to prevent the reenergizationof the initially energized power source after the other power source hasbeen energized.

5. A power transfer system in which any one of at least two powersources can be the primary source of power, comprising at least twopower sources, first means for selectively energizing any one of saidpower sources, second means coupled through said first means to theoutput of said one power source and responsive thereto for energizingsaid other power source when said one power source is not operatingnormally, third means coupled through said first means to the output ofsaid other power source and responsive thereto, when said first meansselects said other power source to be initially energized, forenergizing said one power source when said other power source is notoperating normally, and fourth means coupling said second and thirdmeans together through said first means to prevent the reenergization ofthe initially energized power source after the other power source hasbeen energized.

6. A power transfer system in which any one of at least two powersources can be the primary source of power, comprising at least firstand second power sources, an initiating relay, a selector switch coupledto said initiating relay for coupling either one of said power sourcesto said initiating relay to selectively energize one of said powersources, said first power source having associated therewith a firstrelay responsive to the output thereof and coupled to said selectorswitch and said second power source, said first relay energizing saidsecond power source only when said first power source falls below apredetermined level after being initially activated, said second powersource having associated therewith a second relay responsive to theoutput thereof and coupled to said selector switch and said first powersource, said second relay energizing said first power source only whensaid second power source falls below a predetermined.

level after being initially activated, a third relay associated withsaid first power source and responsive to the output thereof forconnecting a load circuit thereto, and a fourth relay associated withsaid second power source and responsive to the output thereof forconnecting a load circuit thereto, said third and fourth relays beinginterconnected so that operation of either one prevents the operation ofthe other.

7. A power transfer system in which any one of at least two powersources can be the primary source of power, comprising at least firstand second power sources, an initiating relay, a selector switch coupledto said initiating relay for coupling either one of said power sourcesto said initiating relay to selectively energize one of said powersources, said first power source having associated therewith a firstrelay responsive to the output thereof and coupled to said selectorswitch and said second power source, said first relay energizing saidsecond power source only when said first power source falls below apredetermined level after being initially activated, said second powersource having associated therewith a second relay responsive to theoutput thereof and coupled to said selector switch and said first powersource, said second relay energizing said first power source only whensaid second power source falls below a predetermined level after beinginitially activated, and said first relay being coupled to said secondrelay through said selector switch so as to prevent the reenergizationof the initially energized power source after the other power source hasbeen energized.

References Cited in the file of this patent UNITED STATES PATENTS1,646,215 Place Oct. 18, 1927 2,106,968 Dannheiser Feb. 1, 19382,194,822 Dannheiser Mar. 26, 1940 2,468,135 Taliaferro Apr. 26, 19492,482,506 Purifoy et al Septv 20, 1949

